1. Field of the Invention
Non-telecentric emission spatial light modulators, emissive micro-pixel displays, ultra-compact image projectors, directional light modulators, multi-view 2D displays, 3D displays, near-eye displays, head-up displays.
2. Prior Art
Spatial light modulators (SLMs) are a class of optoelectronic devices having a planar array of micro-scale pixels that are typically used as an image source in display systems. Such light modulators typically fall in one of three distinctive categories: reflective, transmissive or emissive. Examples of reflective SLMs include micro mirror array devices and liquid crystal on silicon (LCoS) devices. Examples of transmissive SLMs include high temperature poly-silicon liquid crystal (HTPS) devices. Examples of emissive SLMs include emissive micro-pixel array devices. One example of an emissive micro-pixel array device may be based on the Quantum Photonic Imager or QPI® imager described in U.S. Pat. Nos. 7,623,560, 7,767,479, 7,829,902, 8,049,231, 8,243,770 and 8,567,960 and organic light emitting diode (OLED) micro-pixel array devices. Both reflective and transmissive SLMs typically require an external light source to modulate images while an emissive SLM generates its own light. In general, all current categories of SLMs modulate telecentric light; meaning the modulated light bundles have their chief rays perpendicular to the plane of the light modulator pixel array. In the case of reflective and transmissive SLMs, telecentric light modulation is dictated by the design limitations of their external light source. Telecentric light emission is the only option available for emissive SLMs with a Lambertian emission profile such as OLED based SLMs.
Example micro-emissive solid state light-emitting display elements suitable for use with the embodiments herein include, without limitation, those described in U.S. Pat. Nos. 7,623,560, 7,767,479, 7,829,902, 8,049,231, 8,243,770 and 8,567,960. These SSL imagers feature high brightness, in a multi-color emissive micro-pixel spatial array with all of its needed drive circuitry in a single device. Within the context of this disclosure the term “SSL imager” is henceforth intended to mean an optoelectronics device that comprises an array of emissive micro-scale solid state light (SSL) emitting pixels. The SSL light emitting pixels of such an imager, hereinafter referred to as simply SSL imagers, are typically either a light emitting diode (LED) or laser diode (LD) whose on-off state is controlled by the drive circuitry contained within a CMOS device upon which the emissive micro-scale pixel array is formed or bonded. The pixels within the emissive micro-scale pixel array of an SSL imager are individually addressable through its drive circuitry, such as CMOS or the comparable, enabling an SSL imager to emit light that is modulated spatially, chromatically and temporally. The multiple colors emitted by an SSL imager share the same pixel optical aperture. In an SSL imager best suited for use with the embodiments herein, each SSL imager pixel emits at least partially collimated (or non-Lambertian) light, in the case of a QPI SSL imager, with an angle of divergence ranging, by design, from ±5° to ±45°. The size of the pixels comprising the emissive array of an SSL imager would typically be in the range of approximately 5-20 microns with the typical emissive surface area of the device being in the range of approximately 15-150 square millimeter. An SSL imager preferably can be designed with minimal gap between its emissive pixel array area and the device physical edge, allowing a multiplicity of SSL imagers, including QPI imagers, to be tiled to create any arbitrary size emissive display area.
Although all current categories of SLMs preferably modulate telecentric light, there is much to be gained from a non-telecentric light emission SLM. Since reflective and transmissive SLM's non-telecentric light modulation capability is limited by their external light source, and an emissive OLED-based SLM cannot achieve non-telecentric light emission by virtue of its Lambertian light emission profile, the SSL imager with its emissive multi-color micro-pixels that emits collimated (or non-Lambertian) light is uniquely qualified to achieve non-telecentric light modulation. It is therefore an objective of this invention to extend the design and manufacturing methods of an SSL imager to include the capability of non-telecentric light emission for the numerous possible applications that stand to benefit from such capability, some few of which are described herein by way of non-limiting examples only.
FIG. 1A illustrates the prior art design concept of a projection display that uses a telecentric light emission SLM. As illustrated in FIG. 1A, the divergence pattern of the light bundles 105 emitted from the telecentric emission SLM 110 dictates the use of a large diameter projection optics 115 which typically dictates the large optical track length 120, which in turn makes the overall design of a projection system that uses the telecentric emission SLM 110 overly bulky. It is therefore one of the objectives of this invention to introduce non-telecentric emission SLM methods that enable smaller diameter projection optics, and consequently achieve shorter optical track lengths and a substantially more compact overall projection system.
FIG. 1B illustrates the prior art designs of a 3D light field display that uses a telecentric light emission SLM, for example U.S. Pat. Nos. 8,928,969, 8,854,724 and 9,195,053. In these types of displays, an array of lenses (130-132) are used whereby each of these lenses (130 for example) directionally modulates the light emitted from the sub-array of the SLM micro pixels 115 to subtend into a unique set of directions depending on the spatial position of each pixel within the sub-array of pixels. As illustrated in FIG. 1B, the divergence pattern of the telecentric light bundles 135 emitted from the pixels at the boundaries of each lens (130 for example) corresponding pixel sub-array would partially illuminate the adjacent lenses (131 and 132 for example). This effect, which is often referred to as “cross-talk”, causes undesirable “ghost” distortions in the directionally modulated 3D image. It is therefore another objective of this invention to introduce non-telecentric emission SLM methods that enable a 3D light field display exhibiting minimal cross-talk image distortion.
In the design of 3D displays, directional modulation of the emitted light is necessary to create the 3D viewing perception. In a typical 3D display, a backlight with uniform illumination in multiple illumination directions is required to display images of the same scene from different directions by utilizing some combination of spatial multiplexing and temporal multiplexing in the SLM. In these 3D displays, the light that typically comes from the directional backlight is usually processed by a directionally selective filter (such as diffractive plate or a holographic optical plate for example FIG. 1D, U.S. Pat. No. 7,952,809) before it reaches the spatial light modulator pixels that modulate the light color and intensity while keeping its directionality.
Currently, prior art directional light modulators are a combination of an illumination unit comprising multiple light sources and a directional modulation unit that directs the light emitted by the light sources to a designated direction (see FIG. 1D, 1E & 1F). As illustrated in FIG. 1A, 1B & 1C which depict several variants of the prior art, an illumination unit is usually combined with an electro-mechanical movement device such as scanning mirrors, a rotating barriers (see U.S. Pat. Nos. 6,151,167, 6,433,907, 6,795,221, 6,803,561, 6,924,476, 6,937,221, 7,061,450, 7,071,594, 7,190,329, 7,193,758, 7,209,271, 7,232,071, 7,482,730, 7,486,255, 7,580,007, 7,724,210, 7,791,810 and U.S. Patent Application Publication Nos. 2010/0026960 and 2010/0245957), or electro-optically such as liquid lenses or polarization switching (see U.S. Pat. Nos. 5,986,811, 6,999,238, 7,106,519, 7,215,475, 7,369,321, 7,619,807, 7,952,809 and FIG. 1A, 1B & 1C).
In addition to being slow, bulky and optically lossy, the prior art directional backlight units typically need to have narrow spectral bandwidth, high collimation and individual controllability for being combined with a directionally selective filter for 3D display purposes. Achieving narrow spectral bandwidth and high collimation requires device level innovations and optical light conditioning, increasing the cost and the volumetric aspects of the overall display system. Achieving individual controllability requires additional circuitry and multiple light sources, increasing the system complexity, bulk and cost. It is therefore an objective of this invention to introduce directional light modulators that overcome the limitation of the prior art, thus making it feasible to create distortion free 3D and multi-view 2D displays that provide the volumetric advantages plus a viewing experience over a wide viewing angle.
Additional objectives and advantages of this invention will become apparent from the following detailed description of preferred embodiments thereof that proceeds with reference to the accompanying drawings.